Light guide plates and backlight module

ABSTRACT

A light guide plate includes a body having a bottom surface and a light output surface opposite to the bottom surface. A scattering structure is formed on the bottom surface. The scattering structure includes a plurality of scattering dots located in the form of a plurality of concentric shapes about the center. A backlight module using the light guide plate is also provided.

BACKGROUND

1. Technical Field

The present disclosure relates to a light guide plates and a backlightmodules and, particularly, to a light guide plate for direct-typebacklight module and a direct-type backlight module.

2. Description of Related Art

Currently, because liquid crystal displays (LCDs) are thin, lightweight,long lasting, and consume little power, they are extensively used in avariety of electronic devices. However, liquid crystal displays are notself-luminescent, therefore, backlight modules are typically required.Generally, backlight modules can be categorized as either direct-typebacklight modules or edge-type backlight modules. Because direct-typebacklight modules can provide high illumination in comparison withedge-type backlight modules, direct-type backlight modules are morewidely employed in numerous applications.

A light guide plate for direct-type backlight module according to arelated art includes a top light output surface, a bottom surfaceopposite to the light output surface and at least one side connectingthe bottom surface and the top light output surface. At least one of thebottom surface and the top light output surface includes a center and aplurality of scattering dots. The scattering dots are arranged atrandom. However, a light source, for example, a point light source,usually emits column-shape lights and the light guide plate is in squareor rectangle form. Therefore, the light output from the light guideplate is not uniform, thereby reduces the uniformity of illumination ofthe direct-type backlight module.

What is needed, therefore, is to provide a light guide plate and adirect-type backlight module using the same that have improveduniformity of illumination.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present light guide plate and direct-type backlightmodule can be better understood with reference to the followingdrawings. The components in the drawings are not necessarily drawn toscale, the emphasis instead being placed upon clearly illustrating theprinciples of the present light guide plate and direct-type backlightmodule.

FIG. 1 is an exploded, cross-sectional view of a direct-type backlightmodule in accordance with a present embodiment of the presentdisclosure.

FIG. 2 is a schematic bottom view of the light guide plate of FIG. 1.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate at least one embodiment of the present light guide plate anddirect-type backlight module, in at least one form, and suchexemplifications are not to be construed as limiting the scope of thedisclosure in any manner.

DETAILED DESCRIPTION

References will now be made to the drawings to describe, in detail,various embodiments of the present light guide plate and direct-typebacklight module.

Referring to FIG. 1, a direct-type backlight module 20 according to apresent embodiment is shown. The backlight module 20 includes a lightsource 200, a light guide plate 202, a reflective plate 204, amicroprism plate 206, a polarization plate 208 and a diffusing plate210.

The light guide plate 202 includes a body having a bottom surface 212, alight output surface 214 opposite to the bottom surface 212, and atleast one lateral side 216. The bottom surface 212 has a center 218. Thelight source 200 is located adjacent to the bottom surface 212 andaligned with the center 218. The reflective plate 204 is located betweenthe light source 200 and the bottom surface 212 of the light guide plate202. The microprism plate 206, the polarization plate 208 and thediffusing plate 210 are located in sequence from bottom to top above thelight output surface 214 of the light guide plate 202.

The light source 200 includes a luminescent device 228 and a focusingdevice 230. The luminescent device 228 is a point light source such asfluorescent lamp or light-emitting diode (LED). In one embodiment, theluminescent device 228 is a monochromatic LED, and the focusing device230 includes an aspherical lens and an aspherical mirror. The light beam232 radiated from the light source 200 can almost vertically strike thebottom surface 212 of the light guide plate 202. In one embodiment, adiameter of the light beam 232 ranges from about 6 millimeters to about8 millimeters.

The light guide plate 202 can be a transparent plate in a round, square,rectangle, polygon or other shape. The light guide plate 202 can be madeof plastic, polymethyl methacrylate (PMMA) or glass. The thickness ofthe guide plate 202 is arbitrary, and can be selected according to need.In one embodiment, the light guide plate 202 is a square PMMA plate andthe side length of the light guide plate 202 is about 50 millimeters.

Referring to FIG. 2, the light guide plate 202 includes a scatteringstructure P formed on the bottom surface 212. The scattering structure Pincludes a plurality of scattering dots 220 located on the bottomsurface 212 of the light guide plate 202. The scattering dots 220 arearranged in the form of a plurality of concentric shapes about thecenter 218. The shapes can be round, ellipsoidal or polygonal orcombinations thereof. The adjacent two shapes are located equidistantlyand a distance between the adjacent two shapes ranges from about 0.5millimeter to about 2 millimeters. The density of the scattering dots220 can increase further away from the center 218 to the sides so as tomaintain a uniform light output as the intensity of light reduces awayfrom the center 218 to the sides. The scattering dots 220 on the sameshape are located uniformly. A distance between the adjacent twoscattering dots 220 on the same shape ranges from about 0.1 millimetersto about 1 millimeter. The density of the scattering dots 220 on eachshape can increase further away from the center 218. The scattering dots220 can be protruding, concave or a combination thereof. The shape ofthe scattering dots 220 can be triangular, square, rhombic, round or acombination thereof. Effective diameters of the scattering dots 220range from about 0.1 millimeters to about 0.5 millimeters. Thescattering dots 220 can be made of ink, Ti-related materials or Sicompound. The exposed surfaces of the scattering dots 220 can be coatedwith highly reflective material (not shown). The scattering structure Pis configured to scatter incident light propagating within the lightguide plate 202, and thereby uniformly transmit the light to the lightoutput surface 214 of the light guide plate 202.

Because the light beam 232 radiated from the light source 200 is usuallycolumn-shaped, the scattering dots 220 adjacent to the center 218 can bearranged in the form of a plurality of concentric circles around thecenter 218. The scattering dots 220 adjacent to the edge of the bottomsurface 212 can be arranged in the form of a plurality of concentricpolygons around the center 218. The shape of the polygons can besubstantially the same as the shape of the light guide plate 202. Theratio of the number of circles to the number of polygons can be lessthan 20:1. The scattering dots 220 in an area 234, between the mostoutside of concentric circle and the most inside of concentric polygon,are arranged in a plurality of circular arcs. In one embodiment, thelight guide plate 202 is a square plate with a side length of 50millimeters. There are 15 circles and 5 polygons. The diameter of thefirst circle 240 adjacent to the center 218 can be larger than 8millimeters so that the light beam 232 can directly enter the lightguide plate 202. The last circle 236 is tangential to the first polygon238. A distance between adjacent two shapes is about 1 millimeter. Adistance between the adjacent two scattering dots 220 on the same shapeis about 0.6 millimeters. The scattering dots 220 are half-ball concavedents in the light guide plate. A diameter of the half-ball concave isabout 0.3 millimeters.

In other embodiments, the light guide plate 202 can include a scatteringstructure formed on the light output surface 214 of the light guideplate 202, and the scattering structure includes a plurality ofscattering dots arranged in the form of a plurality of concentric shapesabout the center of the light output surface 214. Alternatively, thelight guide plate 202 can include a first scattering structure formed onthe bottom surface 212 and a second scattering structure formed on thelight output surface 214 of the light guide plate 202. When thescattering structure P is formed at both the bottom surface 212 and thelight output surface 214, the light beam between the bottom surface 212and the light output surface 214 can be reflected many times by thescattering dots 220, thus the uniformity of light output can be furtherimproved.

In one embodiment, the light guide plate 202 further includes areflector 222 located opposite to the center 218. The reflector 222 canbe a protrusion protruding from the light output surface 214 to theinside of the light guide plate 202. The protrusion can be generallyhemispherical or conical. The reflector 222 has a reflective surface224. The reflective surface 224 of the reflector 222 is configured toreflect part of the light from the corresponding light source 200 to theinside of the light guide plate 202. The light reflected into the lightguide plate 202 by the reflective surface 224 can be scattered by thescattering dots 220 and get to the light output surface 214 uniformly.Thus, the uniformity of illumination of the backlight module 20 isimproved. The reflective surface 224 can be coated with reflectivematerial. The reflective material can be selected according to desiredreflective efficiency. The shape of the protrusion is not limited towhat is described and illustrated above. Any suitable shapes that allowthe reflective surface 224 to redirect light into the light guide plate202 may be employed.

The light guide plate 202 provided in the disclosure can be used in abacklight module having different structure with the backlight module20.

The reflective plate 204 is located between the light source 200 and thebottom surface 212 of the light guide plate 202. The shape and the areaof the reflective plate 204 are the same with that of the light guideplate 202. The thickness of the reflective plate 204 is arbitrary, andcan be selected according to need. Part of the reflective plate 204opposite to the light source 200 is transparent or hollow so that thelight eradiated from the light source 200 can enter the light guideplate 202 directly. In one embodiment, part of the reflective plate 204opposite to the light source 200 is hollow. The reflective plate 204further includes a reflective film (not shown) located on the surface ofthe reflective plate 204 opposite to the light guide plate 202. Thelight striking on the bottom surface 212 of the light guide plate 202can be reflected back into the light guide plate 202. Thus, theuniformity of illumination of the backlight module 20 can be improved.

The microprism plate 206, the polarization plate 208 and the diffusingplate 210 are located in sequence from bottom to top above the lightoutput surface 214 of the light guide plate 202. The microprism plate206 is configured to better focus light along desired paths. Thepolarization plate 208 is located between the microprism plate 206 andthe diffusing plate 210. The polarization plate 208 is configured topolarize and modulate the light passing there through. The diffusingplate 210 is configured to enhance the uniformity of distribution oflight that passes from the backlight module 20 to the display panel.

For enhancing reflection efficiency, the bottom surface 212 and lateralside 216 of the scattering dot 220 can be coated with highly reflectivematerial (not shown). In addition, the backlight module 20 can furtherinclude an optical film (not shown), such as a brightness enhancementfilm (BEF) or a light scattering film, located above the light outputsurface 214. The optical film increases the brightness of a displaypanel (not shown) of the LCD device.

In the working process of the backlight module 20, the light radiatedfrom the light source 200 is a column-shape light beam 232. The lightbeam 232 gets through the hollow part of the reflective plate 204 andenters the light guide plate 202. After the light beam 232 arrives atthe reflector 222, part of the light gets out of the light guide plate202 through the light output surface 214. At the same time, the otherpart of the light is reflected by the reflective surface 224 into thelight guide plate 202. The light in the light guide plate 202 isreflected between the output surface 214 and the bottom surface 212until it emmiated out of the light guide plate 202. Because thescattering dots 220 adjacent to the center 218 are arranged on aplurality of concentric circles around the center 218, the scatteringstructure P can scatter the column-shape light beam 232 uniformly to thelight output surface 214. Because the scattering dots 220 adjacent tothe edge of the bottom surface 212 are arranged on a plurality ofconcentric polygons around the center 218, the scattering structure Pcan scatter the light to uniformly light a square output surface 214.Thus, the uniformity of illumination of the backlight module 20 can beimproved. The uniformity of the backlight module 20 can be greater than85%. In one embodiment, the uniformity of the backlight module 20 is90%. The backlight module 20 can be widely employed in Liquid CrystalDisplays.

Finally, it is to be understood that the above-described embodiments areintended to illustrate rather than limit the disclosure. Variations maybe made to the embodiments without departing from the spirit of thedisclosure as claimed. The above-described embodiments illustrate thescope of the disclosure but do not restrict the scope of the disclosure.

1. A light guide plate, comprising: a body having a bottom surfacehaving a center, a light output surface opposite to the bottom surface;and a first scattering structure formed on the bottom surface, whereinthe first scattering structure comprises a plurality of scattering dotsform a plurality of shapes concentrically located around the center. 2.The light guide plate as claimed in claim 1, wherein the shapes areround, polygonal or both round and polygonal.
 3. The light guide plateas claimed in claim 2, wherein the scattering dots adjacent to thecenter are arranged in a plurality of concentric circles, and thescattering dots adjacent to the edge of the bottom surface are arrangedin a plurality of concentric polygons.
 4. The light guide plate asclaimed in claim 2, wherein a ratio of the number of circles to thenumber of polygons is less than 20:1.
 5. The light guide plate asclaimed in claim 2, wherein a second plurality of scattering dots arelocated in an area between the most outside of concentric circle and themost inside of concentric polygon; the second plurality of scatteringdots are arranged in a circular arcs.
 6. The light guide plate asclaimed in claim 2, wherein the polygon is substantially corresponds tothe shape of the light guide plate.
 7. The light guide plate as claimedin claim 1, wherein two adjacent shapes have a distance between themthat ranges from about 0.5 millimeters to about 2 millimeters.
 8. Thelight guide plate as claimed in claim 1, wherein a density of thescattering dots increases further away from the center.
 9. The lightguide plate as claimed in claim 1, wherein the scattering dots on thesame shape are dispersed uniformly, and a distance between adjacent twoscattering dots on the same shape ranges from about 0.1 millimeters toabout 1 millimeter.
 10. The light guide plate as claimed in claim 1,wherein a density of the scattering dots on each shape increases furtheraway from the center.
 11. The light guide plate as claimed in claim 1,wherein the exposed surfaces of the scattering dots are coated withreflective material.
 12. The light guide plate as claimed in claim 1,further comprising the a second scattering structure formed on the lightoutput surface, the second scattering structure comprising a pluralityof scattering dots arranged on a plurality of concentric shapes around acenter of the light output surface.
 13. The light guide plate as claimedin claim 1, further comprising a reflector located opposite to thecenter; the reflector protrudes from the light output surface to theinside of the light guide plate.
 14. A light guide plate, comprising: abody having a bottom surface having a center, a light output surfaceopposite to the bottom surface; and a scattering structure formed on thelight output surface, and the scattering structure comprises a pluralityof scattering dots arranged in the form of a plurality of concentricshapes about the center of the light output surface.
 15. A backlightmodule comprising: a light guide plate including a bottom surface, alight output surface opposite to the bottom surface; a light sourcelocated adjacent to the center of bottom surface; and at least onescattering structure formed on the bottom surface or the light outputsurface, and the scattering structure comprises a plurality ofscattering dots arranged in the form of a plurality of concentric shapesabout the center or the center light output surface.
 16. The backlightmodule as claimed in claim 15, further comprising a reflective platelocated between the light source and the bottom surface of the lightguide plate.
 17. The backlight module as claimed in claim 16, whereinthe reflective plate comprises a reflective film located on a surface ofthe reflective plate.
 18. The backlight module as claimed in claim 15,further comprising a brightness enhancement film located above the lightoutput surface of the light guide plate.
 19. The backlight module asclaimed in claim 15, further comprising a light scattering film locatedabove the light output surface of the light guide plate.
 20. Thebacklight module as claimed in claim 15, further comprising a microprismplate, a polarization plate and a diffusing plate.